<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>案例</title>
    <style>
        .backTop{
            position: fixed;
            font-size: 20px;
            width: 40px;
            height: 80px;
            border: 2px solid black;

            right: 20px;
            bottom: 100px;
        }
    </style>
</head>
<body>
<div style="height: 10000px;text-align: center">
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</div>
<div class="backTop">^^返回顶部</div>
</body>
</html>